A339571 A133058 with duplicates removed.

1, 4, 8, 2, 12, 3, 24, 16, 21, 7, 27, 48, 32, 30, 15, 5, 34, 64, 36, 18, 54, 41, 80, 120, 45, 59, 104, 150, 75, 123, 91, 142, 194, 97, 151, 206, 262, 131, 189, 248, 308, 77, 139, 202, 266, 133, 199, 334, 167, 237, 380, 95, 169, 244, 320, 158, 79, 82, 164, 86

Offset

1,2

Links

Table of n, a(n) for n=1..60.

Dana G. Korssjoen, Biyao Li, Stefan Steinerberger, Raghavendra Tripathi, and Ruimin Zhang, Finding structure in sequences of real numbers via graph theory: a problem list, arXiv:2012.04625 [math.CO], Dec 08, 2020. See Section 2.6.

Mathematica

DeleteDuplicates@ Block[{a = {1, 1}, k = 1}, Do[AppendTo[a, If[# == 1, a[[-1]] + i + 1, a[[-1]]/#]] &@ GCD[a[[-1]], i], {i, 2, 80}]; a] (* Michael De Vlieger, Dec 09 2020 *)

Prog

(PARI) lista(nn) = my(v=List([1]), x=1, y); print1(1); for(n=2, nn, if(!setsearch(Set(v), x=if(1==y=gcd(x, n), x+n+1, x/y)), print1(", ", x); listput(v, x))); \\ Jinyuan Wang, Dec 12 2020
(Python)
from math import gcd
from itertools import count, islice
def A339571_gen(): # generator of terms
    a, aset = 1, {1}
    yield 1
    for n in count(2):
        a = a+n+1 if (b:=gcd(a, n)) == 1 else a//b
        if a not in aset:
            aset.add(a)
            yield a
A339571_list = list(islice(A339571_gen(), 30)) # Chai Wah Wu, Mar 18 2023

Crossrefs

Cf. A133058.

Sequence in context: A088609 A163813 A109815 * A110653 A052309 A332905

Adjacent sequences: A339568 A339569 A339570 * A339572 A339573 A339574

Keyword

nonn

Author

N. J. A. Sloane, Dec 09 2020

Extensions

More terms from Jinyuan Wang, Dec 12 2020

Status

approved